Multiple-channel inductive heating apparatus



p 13, 1945- s. s. SCHNEIDER ET AL 2,335,031

MULTIPLE-CHANNEL INDUCTIVE HEATING APPARATUS Filed April 27, 1945 w l F enerafar WITNESSES:

Patented Sept. 1 1945 MULTIPLE-CHANNEL INDUCTIVE HEATING APPARATUS Stanley 8. Schneider, Halethorpe, and Luther W.

Gregory, Baltimore, Md., asslgnors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation oi Pennsylvania I Application April 27, 1943, Serial No. 484,684

3 Claims. ((1219-13) Our invention relates to apparatus for simul taneously inductively heating a plurality of elec-' trically conductive, and preferably magnetizable, wires, strips, or other objects, preferably elongated articles which are substantially continuously moving in the direction of their length, while passing through the inductive heating coil. Our invention has particular relation to the inductive heating oi fine wires, or other objects which, by reason oi their small size, or pecularities oi shape, make it dimcult to build an inductive heating coil of such size or shape that the object or objects to be heated make up a reasonable proportion of the total cross sectional area encircled by the coil, or in applications where considerable diillculty from the standpoint of corona would be encountered if only one object were heated at a time,

A more specific object oi our invention is to provide an inductive heating apparatus in which an insulating means is provided within the inductive heating coll, said insulating means having a plurality of separate holes, each surrounded by insulatin walls, for receiving the several articles to be heated, which articles may be iron -or steel wires, or thin strips, or electrically conductive articles of other shapes and materials. In this way, a separate space or channel is provided for each of the several objects which are to be inductively heated, preventing said objects from being welded together or otherwise coming into contact with each other or with the inductive heating coil. 7

We have found, in the iorms in which we have heretofore used our invention, that no diiilculty is discernible from the standpoint of any unequal distribution of the magnetic fluxes, and hence the inductive heating, among the several objects being passed simultaneously through the inductive heating coil; while the tendency to produce corona is very considerably reduced by the presence of a plurality of spaced objects, which have a corona-effect approaching the generaloverall contour of the whole assembly of objects, as distinguished from a corona-effect which is characteristic of the size or shape of each individual object being heated. At the same time, the utilization of a multiple-channel insulating material or guard or guide-means makes it possible to more economically utilize the cross-sectional area embraced by the heating-coil, thus improving the ratio of kilowatts to kilovolt-amperes, thus increasing the overall eiliciency oi the heating.

With the foregoing and other objects in view,

our invention consists in the apparatus, parts, to

combinations, assemblies, systems, and methods hereinaiter described and claimed, and illustrated in the accompanying drawing, wherein Figure 1 is a diagrammatic plan-view oi circuits and apparatus illustrating our invention in an exemplary embodiment, with parts broken away to illustrate the construction, and

Fig. 2 is a cross-sectional view on the line 11-11 of Fig. 1.

In the form oi embodiment of our invention shown in the drawing, we utilize a single inductive heating coil t'through which seven wires 4 are passed simultaneously, in order to heat the wire to the Curie point (about 1400" 1".) or to any other desired temperature. .The number of wires to be simultaneously heated is not critical: neither is the shape or the size of the wires or other objects to be heated, which might well be thin strips, ior example tinplated strips, or a plurality oi metal or conducting articles of any size or description. While we particularly have in mind iron or steel wires or other magnetizable objects, our invention is not altogether limited to the use of magnetizable materials, so long as the irequency oi the inductive heating current is properly chosen. We have also particularly had in mind the heating of small-diameter wires in the range from a diameter of 0.005" to a diameter of 0.035", although here, again, we are not limited to any particular diameter, ,or even to a cylindrical shape such as is characteristic oi wires.

In accordance with our invention we provide an insulating member I which is provided with a plurality oi separate holes I, one ior each wire 4 or other elongated object being heated, said holes running lengthwise through the coil, substantially parallel to each other and substantially parallel to the axis of the coil 8. The insulating member I preferably has an axial extent somewhat longer than the coil 8, so that it extends a short distance beyond each end of the coil. The several axially extending holes C are thus each surrounded by insulating walls, so as to eilectually prevent the several wires I from coming in contact with each other, or in contact with the coil I.

The insulating member I, with its axially extending holes 8 therein, can be constructed or iabrlcatcd in any desired manner. When the objects to be heated are wires. as illustrated, so that the holes will be cylindrical in cross section (being preferably considerably larger than the wires) an economical and convenient'manner oi iorming theinsulatingbodylistoprovideabundleoi insulatingtubes Loneioreachwiraseidtubes being suitably cemented or bound together in a substantially integral mass.

The several wires 4 are fed into and through the several perforations 6 of the insulating body 5 within the heating coil 3 from individual spools or rolls 8, and are re-wound upon other spools or rolls 9 which are driven by electrical motors Ii, preferably in such a manner that all of the wires 4 pass through the inductive heating coil at the same rate.

The inductive heating coil 3 is preferably made of copper tubing, through which water, or other liquid coolant, is circulated, as indicated by the arrows l3 and H. Alternating-current electrical energy is furnished to the terminals of the coil 3, as by means of an oscillation generator i5, which is indicated symbolically in Fig. 1. While the necessary or desirable frequency of the electrical supply is not extremely critical, nevertheless the frequency should be in the correct range, dependent upon the resistivity of the heated material, and other factors. The optimum frequency is also inversely proportional to the square of the diameter or thickness of the material being heated. For example, for iron wires of 0.005" diameter, the optimum frequency is probably somewhere in the range of 1.5 times 10 cycles per second, although frequencies wh ch are a considerable percentage higher or lower might readily be utilized. This frequency is intended for heating the wire up to the Curie point. For a lower temperature of heating, a lower frequency would be perhaps more suitable, whereas, for temperatures in excess of the Curie point, or for wires or strips of non-magnetizable conductive materials, considerably higher frequencies would be required.

In operation, a plurality of wires or strips of the same diameter or gage are caused to move continuously through the same heating coil at a constant or predeterminably controllable speed, while the coil is energized with high-frequency current of a suitable frequency. The alternating magnet c flux of the coil, flowing ax ally, traverses all of the wires or strips 4, thus inducing circulating currents which heat the wires or strips by reason of the resistivity of the material to be heated. The length of the coil 3, and its ampere-turns, are so chosen, with respect to the amount of material to be heated per second. that the wires or strips 4 reach their predetermined, desired temperature while passing through the coil at the speed which is determined by the energization of the reeling-motors II. By causin more than one wire or strip to pass through the coil 3 at the same time, the cross-sectional space within the coil-turns is utilized more efflciently, so that a larger percentage of the flux of the coil is put to useful work by being caused to traverse material to be heated.

The amount of electrical energy necessary to heat the wire or strips may be quite large, particularly at high speeds of travel of the wire or strips. On the other hand, the amount of current which can be utilized in the coil is limited by the amount of magnetizing force which can be efliciently utilized, so that the voltage of the coil is quite likely to be so high that measures must be adopted to avoid trouble from corona. Under these circumstances, the utilization of a plurality of fine wires, or other elongated materials to be heated, is a distinct advantage because the electrostatlc field surrounding the group of spaced wires or other elongated members produces a corona-efiect which approaches the corona-eflect which is obtainable from a solid conductor having about the same diameter as the periphery of the bundle or group of spaced parallel wires. Since the corona-effect is dependent upon the wire-diameter, being very much greater for smaller wires than for large cylinders, our use of a bundle of spaced parallel wires provides a construction which is relatively free of corona, as distinguished from the very intense and troublesome corona which would be expectable from the use :f a single wire within the inductive heating coil While we have described our invention in only one form of embodiment, which is at present preferred, we wish it to be understood that our invention is susceptible of other forms of embodiment, and perhaps of other practical limits than those which have been here'nabove described. We desire, therefore, that our appended claims shall be accorded the broadest interpretation consistent with their language.

We claim as our invention:

1. Means for simultaneously inductively heating a plurality of electrically conducting articles, comprising the combination of insulating means substantially devoid of conducting material for providing a plurality of separate holes, each surrounded by insulating walls substantially devoid of conductive material, for receiving the several articles, an inductive heating-coil surrounding said insulating means, and means, including coilterminals, for feeding alternating current into said coil.

2. Means for simultaneously inductively heating a plurality of elongated electrically conducting articles while they are substantially continuously moving in the direction of their length, comprising the combination, with the means for keeping said articles moving in the direction of their length, of insulating means substantially devoid of conducting material for providing a plurality oi separate, substantially parallel, holes, each hole being open at both ends and being surrounded by insulating walls substantially devoid of conductive material, for receiving the several articles, an inductive heating-coil surrounding said insulating means, the axis of the coil being substantially parallel to said holes, and means, including coil-terminals, for feeding alternating current into said coil.

3. Means for simultaneously inductively heating a plurality of electrically conducting wires while they are substantially continuously moving in the direction of their length. comprising the combination, with the means for keeping said wires moving in the direction of their length, of insulating means substantially devoid of conducting material for providing a plurality of separate, substantially parallel, holes, each hole being open at both ends and being surrounded by insulating walls substantially devoid of conductive material, for receiving the several wires, an inductive beating-coil surrounding said insulating means, the axis of the coil being substantially parallel to said holes, and means, including coil-terminals, for feeding alternating current into said coil.

STANLEY B. SCHNEIDER. LUTHER W. GREGORY. 

